Method of making rotary gear cutters



Sgpt. 12, 1939. 'w 5, PRAEG 2,172,545

METHOD OF MAKING ROTARY GEAR GUTTERS Filed June 21, 1937 2 Sheets-SheetlHas,

INVENTOR WALTER s. PRAEG.

W W M ATTORNEYS Sept. 12', 1939. w. s. PRAEG METHOD OF MAKING ROTARYGEiAR GU'I'TERS 2 Sheets-Sheet 2 Filed June 21, 1937 FIG. I4.

FIG. l3.

INVENTOR" WALTER s. PRAEG.

um Auwmm ATTORNEYS Patented Sept. 12, 1939 UNITED STATES amnion o AxmGROTARY ou'r'mas Walter S. Praeg, Detroit, Micln, assignor to NationalBroach A: Machine-Company,

Mich., a corporation Application June 21,

1 Claim.

This invention relates to a rotary gear cutter and more particularly toa rotary gear cutter which is in the form of a gear having teeth ofgenerally involute. contour and having cutting edges provided on thefaces of these teeth by forming grooves in these faces.

The prime object of the present invention is to produce cutters of thistype by a new method of manufacture which comprises separately formingindividual teeth, heat-treating said teeth to harden them, thereaftergrinding thegrooves in the faces of said individual teeth and fln'allyassembling said teeth in'a blank.

Further objects will be apparent'on reading the following detaileddescriptiontaken in'conjunction with the accompanying drawings, inwhich-'- I Fig. 1 15a fragmentary perspective of the type of cutter towhich my invention relates; V

Fig. 2 is a fragmentary end view of a portion of a cutter showing aninserted tooth;

Fig. 3is a fragmentary end view of a cutter .showing a modified insertedtooth Figs. 4 to 7 inclusive are fragmentary'views 0;, of variousmodified forms of inserted teeth;

Figs. 8 to 11 inclusive are fragmentary end views of cutters showingvarious other modified forms of inserted teeth;

Fig. 12 is a fragmentary sectional View of another modified form ofinserted tooth;

Fig. 13 is a fragmentary section of another form of inserted tooth;

Fig.14 is a fragmentary end view of the cutter shown in Fig. 13, and

Figs. 15 and 16 are fragmentary and views of two other inserted teethcutters.

The type of cutter illustrated in Fig. 1 as heretofore made comprises adisk I of high speed steel with teeth 2 cut on the periphery thereof andwith these teeth modified in various manners to provide cutting edges onthe faces of the teeth. A tool of this type is diflicult to make, itbeing particularly difilcult to machine grooves 3 in the faces of thegear teeth. Also, the material of the tooth is relatively expensive. Asa matter of fact, it would be preferable to make the body portion of thegear of some other material less expensive but at the same time bet teradapted for its purposes. For this reason it will be seen that it ishighly advantageous to provide inserted teeth. By this means the teethmay be formed separately of high speed steel and when forming each toothseparately, it is relatively easy to grind the serrations in the facesof the teeth. Thus marked economy Detroit, of Michigan v 1987, SerialNo. 149,510

may be practiced by manufacturing these cutters with inserted teeth,both for the reason that the material of the cutter blank is lessexpensive and because the expense of forming the "teeth is lessened dueto the fact that they may be more easily machined when separated fromthe blank. Furthermore, ground serrations are superior to serrationsformed by other, methods, giving smooth, accurate sides 'on the gashes.

Another highly advantageous featureof inserted teeth in this type ofcutter resides in the replaceability of the teeth. As before stated,these tools are relatively expensive and it' has heretofore beennecessary whenia single tooth became damaged, to replace the whole tool.

I have illustrated in the accompanyingfigures various modified forms ofinserted teeth. In order-to provide inserted teeth in acutter of thistype, it is necessary'first to provide a construction which will insurethat the teeth are very rigidly and firmly held in place in the cutterwhen in use. This is necessary'because any flexibility introduces errorsin the product. The rigidity of the cutter is therefore desirablygreater than the rigidity of the gear being out. It is also necessary toprovide for removal of the teeth for replacement and repair. 7

In the modification illustrated in Fig. 2, I form a cutter blank or bodyID of suitable alloy steel and with oil clearance recesses II formedaround the periphery thereof, The material between adjacent oil recessesforms the support for the inserted tooth. As shown in this figure, Iform a dove-tailed slot in this portion of the blank. The tooth I2 inthis case, as in all modi fications, is formed of high speed steel andis properly shaped and treated before it is assembled into the blankII]. In practice, the tooth I2 will be formed with a suitable generallyinvolute contour on the faces thereof, will be heat treated and then theserrations I3 will be ground in the face of the tooth. The tooth has acooperating dove-tailed tongue portion'lfi adapted to fit snugly withinthe dove-tail slot or groove I4 cut in the blank. The blank is' heated,the inserted tooth is placed in position and the blank is shrunk on tothe tongue I6 of the inserted tooth. In order to provide furthersecurityI propose to spot weld the tongue I6 to the blank II), as indicated atI5 in Fig. 2. I

Fig. 3 is a modification somewhat similar to Fig. 2 and differs chieflyin the fact that instead of a dove-tail portion I6 the tongue 26 isrectangular. In this form the blank 20 is formed with peripheral oilclearance recesses 2| and the teeth as indicated at 23.

in finishing is to finish grind the outsides of the teeth. This willinsure proper spacing, lead, etc.

In Fig. 4 I have illustrated a modified form in' which the body In issubstantially wider than the width of the tooth l2. The tongue, i6 ofthe tooth member is of the same width as-the blank..

This will insure that when the tongue I6 is shrunk into the blank in, itwill be maintained rigidly therein, even though in operation the portionof the tooth member more closely adjacent the tooth proper becomesheated. The additional width of the blank and tongue portion i6 alsoprovides additional strength irrespective of any possible heating of themembers in use. This modification and the modifications of Figs. 5 and 6are practiced with either of the modifications illustrated in Figs. 2 or3, or Figs. 8-11, to be later described. I

Fig. 5 illustrates ;another modification of {the detail illustrated inFig. 4 In this form, the slot I4 is of considerably greater length thanthe width of the tooth'proper I2, but does not extend completely acrossthe blank ill. A shoulder H is left at one end of the slot i4 and thetongue at one end of the blank Hi". This modification is.

particularly useful in certain jobs such as shoulder cutting.

sun another modification is illustrated in Fig.

7 in which the body 30 is provided with a recess 3i which is closed atboth ends by shoulder portions 36. The tooth member comprising a toothproper 32 and a tongue member 34 is placed in this recess. The tongueportion 34 has beveled ends as can be readily seen, and a tapered clamp35 is driven into the tapered recess left between the tongue 34 and theshoulder 36, or as an alternate, the portion 35 may represent weldedmaterial binding the parts together.

I have illustrated still another modification of my invention in Fig. 8.In this figure the blank 40 has recesses 45 formed therein. Betweenthese recesses are 011 clearance grooves 4|. In the body of the blankbetween the recesses 45 and beneath the recesses 4i are holes 44. Ifdesired, the material between the recess 41 and the hole 44 may be slitas indicated at 41. The other member comprises the tooth proper 42 andthe tongue 46, the tongue 46 fitting closely within the recess 45. Inorder to provide the necessary clamping means, tapered pins indicated at48 are driven in the holes 44, thereby wedging the tongues 46 rigidly inplace. These teeth have serrations indicated at 43.

Another modification of my invention is illustrated in Fig. 9 in whichthe blank 50 has a recess 55 formed therein. This recess 55 hassemi-circular portions 54 in the sides thereof as clearly shown. Thetooth member comprising the tooth proper serrated at Hand the tongueportion 55, is inserted with the tongue 56 snugly received in the recess55. Tapered pins 51 are then driven into the semi-circular recessees 54,bearing against the side portions of the tongue 56 and rigidly clampingthe tooth in position.

- In Fig. 10 I have illustrated yet another modification. of myinvention particularly adapted for gear cutters of small diameter. Inthis form I provide for inserting two teeth at a time. The blank BO isprovided with a. dove-tail recess 6'! and suitable oil clearancerecesses H are formed 'in the .periphery thereof. The two adjacent teethadapted to be inserted together are formed as shown in this figure. sothat when assembled their tongue portions 62 together comprise a singledove-tailed tongue portion adapted to be received within the dove-tailgroove 61 in the blank. At the bases of two adjacent teeth abutting eachother is formed an oil clearance 64.- It is contemplated in this formthat the tongues 62 will be retained in position by shrinking the blank.It is further contemplated to insure the rigidity of the assembleddevice by spot welding asint'iicated'at66. v ,5 I 4 I haveillustratedanother modification of my improved insertedtooth gear cutterin Fig. 11. In thls'formthefblank 10 is' provided with a recess 1|, withsemi circular recesses 11 formed in the side wallsof the recess IL. Thetooth membercomprisesatooth proper l2 serrated at 13 and a tongue member14. It will be noted that the tongue portion" has semi-circular recesses15 adapted when thetoothis in inserted position to be complementaryto'the semi-circular recesses 11. Tapered pins I6 are then driventhrough the blank engaging both the blank and the tongue 14 and rigidlysecuring the tooth in assembled position.

Finally, in Fig. 12 I have illustrated another form. of my inventioncomprising a blank 10' in which a recessll' is provided. This recessdoes not extend clear, across the width of the blank, shoulders 13'being left'at each side thereof. The inserted tooth member comprises atooth proper'IZ'and tongue. I8. As will be noted, the tooth proper-"12'is of thesamewidth as the blank, but thetongue portion 'lfiis of lesserwidth and is receivedby the recess H. The shoulders 13 have screwthreaded openings 14 therein adapted to receive screws 11' which engagea recess 15' suitably formed in the tongue portion of the tooth member.V Another modification is illustrated in Figs. 13 and 14. In this formthe blank is provided with peripheral. slots 84, extending across theblank at an angle corresponding to the desired helix angle. On bothfaces of the blank, annular recesses 8| are formed, leaving shouldersadjacent the botom of slots84. The teeth to be inserted, comprising atooth' portion 82 and a tongueportion 86, areseparately formed, andserrations 83 are ground on the faces of the tooth portions. slots 84,and bolt 85 is screwed into the tongue through.asuitableaperture in theshoulder ad- Jacent the bottom of the slot. As illustrated inthesefigures, the tooth portion 82 is of less axial extent than the tongue86. This, however, is optional, and the tooth may, in this as in theother forms, be of the same width as the tongue, or of lesser width andpositioned either centrally or eccentrically on the tongue portions.

I have illustrated yet another embodiment of The tongues 86 are theninserted in my invention in Figure 15. Here the blank 00 has peripheralslots 94. The tooth has a tooth portion 92, serrated at 90, and a tongue96. A portion of the tongue has serrations or saw teeth as at 95.Adjacent the slot and opening into it is a drilled hole 91. Aftergrinding the serrations in the face of the teeth, the tongue is insertedin the slot, and a tapered pin 0| is driven in the hole 91. The materialof the pin being softer than the serrations 05, the pin is deformed toconform therewith, and a tight lock results.

. Fig. 16 illustrates another embodiment of my invention. Here the blankI00 has peripheral slots I04 formed therein. The inserted teeth,comprising tooth portions I02, serrated at I03, and tongue portions I00are inserted. The upper portion of the tongue I02 is inclined, as atIOI. Suitably shaped locking means I01 engage these inclined surfaces,and clampingly lock the teeth in place through the medium of suitablesecuring means III.

It is desired to emphasize at this time the importance of grinding theserrations in inserted teeth. Prior to my invention, it has beennecessary to form the serrations by means of expensive special macl'unesand the results obtained were necessarily inferior to ground serrations.Ground serrations exhibit superior smoothness and accuracy. This isimportant because the cutting edges of the tool are formed by theintersection of the serrations and the face of the tooth. Ob-

viously, greater accuracy and superior iinish in the serrations willimprove the cutting edges, and this improvement will be retainedthroughout the life of the tool.

All of these modifications provide for ready assembly of the tool andfor the removal oi! a single tooth if necessary. A tool made accordingto this invention retains all of the advantages of the integral toolformerly used and in addition has the advantages pointed out above, thatis, economy in manufacture, separate grinding of the serrations in thetooth and replacement oi damaged teeth.

For purposes of illustration, I have shown and described a number ofmodifications of specific cutters, but it will be apparent that themethod defined is applicable generally to any serrated tooth rotary gearcutter.

What I claim as my invention is:

The method oi making gear cutting tools in the form of bodies havingteeth provided with cuttin edges thereon, comprising forming recesses inthe tool body, forming separate tooth members with tooth portions ofdesired contour and tongue portions on the bottom thereof, heat treatingsaid teeth, grinding grooves in the faces 0! said teeth generally fromtop to bottom thereof to provide cutting edges thereon, placing saidtongues in said recesses, and rigidly securing said tongues in saidrecesses.

WALTER. 8. mm.

